This project is concerned with the regulation of events in the cell cycle of a primitive eucaryotic organism, the acellular slime mold Physarum polycephalum. The control of nuclear division and DNA synthesis is studied using metabolic inhibitors and cell fusion. The synthesis and degradation of hundreds of cellular proteins is studied by the technique of two-dimensional gel electrophoresis, which separates proteins according to size and molecular weight. The appearance of specific proteins during the cell cycle is followed by enzyme activity assays and two-dimensional gel electrophoresis. Finally, mathematical models of cellular control systems are constructed and analyzed. The goal of these experimental and theoretical studies is a better understanding of the mechanisms whereby cells control the DNA-to-mass ratio, the timing of nuclear and cell division, and the synthesis and degradation of specific proteins.